sl2018-659

Service Letter SL2018-659/JAP
Action code: WHEN CONVENIENT
Dear Sirs
Operation on very-low and ultra-low sulphur fuel oil (VLSFO and
ULSFO) is becoming more frequent.
Since 2015, operation in SECAs (sulphur emission controlled areas)
has been restricted to operation on 0.1% S fuel or lower. The number
of dual fuel engines in operation on ULSF mixtures and, from 2020,
also the compliant 0.5% S fuel will be increasing.
The owners of engines operated on VLSFO and ULSFO may face
certain challenges with scuffing between the cylinder liner and piston
rings. Operation on gas or other low-flashpoint fuels containing no
sulphur gives challenges similar to those faced when operating on
ULSFO in a SECA or on 0.5% S fuel. Prolonged operation on these
fuels may lead to bore polished liner surfaces with a subsequent risk
of liner scuffing as the consequence.
To increase the margin against damage to the piston rings and cylinder
liners, which will lead to overhaul on short notice, we have introduced
a piston ring configuration that incorporates the hard cermetcoating
on the running side of all piston rings. Cermet-coating on
the piston ring running surface increases the reliability of the main
engine. In many cases, the cermet-coated rings continue to perform
after an episode with momentary oil film breakdown, provided the oil
film is restored. This ensures that the engine can continue in normal
operation until the next planned overhaul. As 2020 is approaching,
we recommend that introduction of this new ring configuration is
done at the next overhaul.
Cermet-Coated Piston
Rings for Operation on
Low-Sulphur Fuels
(0.5% S or lower)
Including LNG, LPG, methanol and ethane
Replaces SL2017-633/JAP
SL2018-659/JAP
March 2018
Concerns
Owners and operators of MAN B&W
two-stroke marine diesel engines.
Type: MC/MC-C, ME/ME-C, ME-B, ME-
GI, ME-GIE and ME-LGI
Summary
New hard cermet-coated piston rings for
continued operation on low-sulphur fuel
(0.5% or lower).
Reference is made to: SL00-382/JSB,
SL12-562/JAP, SL2014-593/DOJA,
SL2014-587/JAP and SL2016-611/JAP.
Send an email to: PrimeServ-cph@mandieselturbo.com if you have
further questions about ordering new piston rings.
Yours faithfully
Mikael C Jensen
Vice President, Engineering
Stig B Jakobsen
Senior Manager, Operation
Head office (& postal address)
MAN Diesel & Turbo
Teglholmsgade 41
2450 Copenhagen SV
Denmark
Phone: +45 33 85 11 00
Fax: +45 33 85 10 30
info-cph@mandieselturbo.com
www.mandieselturbo.com
PrimeServ
Teglholmsgade 41
2450 Copenhagen SV
Denmark
Phone: +45 33 85 11 00
Fax: +45 33 85 10 49
PrimeServ-cph@mandieselturbo.com
Production
Teglholmsgade 35
2450 Copenhagen SV
Denmark
Phone: +45 33 85 11 00
Fax: +45 33 85 10 17
manufacturing-dk@mandieselturbo.com
Forwarding & Receiving
Teglholmsgade 35
2450 Copenhagen SV
Denmark
Phone: +45 33 85 11 00
Fax: +45 33 85 10 16
shipping-cph@mandieselturbo.com
MAN Diesel & Turbo
Branch of MAN Diesel & Turbo SE,
Germany
CVR No.: 31611792
Head office: Teglholmsgade 41
2450 Copenhagen SV, Denmark
German Reg.No.: HRB 22056
Amtsgericht Augsburg

Service Letter SL2018-659/JAP
Operation on low-sulphur fuels (LSFO, VLSFO and ULSFO)
Under normal conditions, when operating on fuel containing
sulphur, the sulphuric acid formed during the combustion
process is condensed on the liner surface, which will ensure
a controlled amount of corrosion. This causes the liner surface
to sustain an adequate level of wear that ensures a high
number of open graphite lamellas in the cast iron matrix.
When operating on low-sulphur fuel, the level of corrosion is
very low and the liner wear is negligible in most cases. Over
time, this will lead to polishing of the running surface. When
the liner surface is smeared, the open graphite lamellas are
closed making it difficult to sustain a proper oil film. Operation
on low-sulphur fuels thus increases the risk of bore polishing
of the liner running surface.
When the oil film is compromised, the cast iron piston rings,
which are in contact with the cast iron liner, may generate high
friction due to metal-to-metal contact and, eventually lead to
liner scuffing. During scuffing, the surface of the liner is hardened
and will need machining before new rings can be run-in.
Cermet-coated piston rings
Cermet is a composite, part-ceramic, part-metal material. It
combines the best properties of a ceramic, i.e. high temperature-resistance
and hardness, with those of a metal.
When applying hard cermet-coating to the piston ring running
side, see Figs. 1 and 2, the margin towards scuffing
increases. The cermet will recover after an incident, provided
the situation is timely discovered and action is taken
to ensure that the development is stabilised. This requires
increased lubrication and a reduction of the load (SL2014-
587/JAP). However, the liner may need machining at the next
overhaul to ensure proper running-in of the new rings.
Fig. 1 shows a three high-ring configuration for piston
crowns with three grooves. To order the piston rings see the
attached plate 8872-2272-0010. A three-ring configuration
with one high- and two low-rings for piston crowns with four
grooves, is also available, see attached plate 8872-2272-
0011. When using a three-ring configuration for a crown with
four grooves, the lowest groove must be left empty, see
SL2016-611/JAP. Fig. 2 shows the 2020 CPR ring pack, see
also plate 8872-2272-0005.
Please note that for 50 bore engines and smaller, the cermet CPR
top rings will be of the CPR-CL not the CPR-POP type as before. For
more information on the CPR-POP type please see SL12-562/JAP.
Double S-lock
Double S-lock
Alu coating
Alu coating
High ring
CL-groove
Cermet
CL-groove
Cermet
Low ring
High ring
Low ring
High ring
Low ring
Oblique
cut
Fig. 1: The CPR ring pack containing three high rings with cermetcoating
on all rings for pistons with three grooves. This ring pack is
also available in a configuration with one high and two low rings.
Fig. 2: The 2020 CPR ring pack containing one high ring and three
low rings with cermet-coating on all rings.
Cermet-coated Piston Rings for Operation on Low-Sulphur Fuels. Page 2 of 3 pages

Service Letter SL2018-659/JAP
New engines
When ordering new vessels, we recommend cermet coating
on all rings to prepare for operation on 0.5% S fuel.
Engines in service on VLSFO or ULSFO
If the engine is already operating on VLSFO or ULSFO fuel,
or if it is intended to do so after 1 January 2020, we recommend
to install cermet-coated rings at the next scheduled
overhaul.
During overhaul it is important to evaluate the liner surface.
If it appears to be polished, machining of the liner surface
may be needed to open up the surface and facilitate easy
running-in of the new piston rings. If the wave-cut surface
has been worn away, it can be re-freshened by wave-cut
grinding.
Engines fitted with SO x
scrubbers
Engines fitted with exhaust gas scrubbers can continue to
operate on high-sulphur fuel after 2020. Omitting cermetcoated
rings is thus an option for some engines. However,
cermet-coated rings are standard for new large-bore engines,
also if operating on high-sulphur fuels.
Lubrication
It is very important to keep a correct level of lubrication and
not to overdose, both when operating on high-sulphur fuel as
well as on VLSFO and ULSFO. Lubrication according to the
adaptive cylinder-oil control (ACC) scheme (feed rate factor
multiplied with the sulphur percentage of the fuel) is recommended.
Otherwise, polishing of the liner surface may occur
and, thereby, increase the risk of seizures, see SL14-587/JAP
or the latest guidance on lubrication.
Piston cleaning (PC) ring
The deposits that build up on the piston crown have a big
influence on liner polishing and smearing. Most engines
built after year 2000 have PC rings installed in the top of the
liner to scrape away deposits which build up on the piston
crown topland. PC rings are recommended for all engines
and can be retrofitted on most older engines. If needed
contact MAN Diesel & Turbo for further details. Furthermore,
check the liner wear after honing, if it is too large, the PC ring
should be omitted or a dummy ring be fitted, see SL00-382/
JSB.
Cermet-coated Piston Rings for Operation on Low-Sulphur Fuels. Page 3 of 3 pages

MAN B&W 8872-2272-0005
2016-01-08 - en
Operation on very-low and ultra-low sulphur fuel oil
Plate Special Instruction
8872-2272-0005
1 (2)

8872-2272-0005 MAN B&W
Plate Special Instruction
8872-2272-0005
Item No. Qty Item Designation
510 - Piston ring, cermet type 1)
522 - Piston ring, cermet type 1)
534 - Piston ring, cermet type 1)
546 - Piston ring, cermet type 1)
Note:
1)
When ordering, please state IMO no., engine type and
height of each ring.
2016-01-08 - en
2 (2)

MAN B&W 8872-2272-0010
Plate Special Instruction
8872-2272-0010
1 (2)

8872-2272-0010 MAN B&W
Plate Special Instruction
8872-2272-0010
Item No. Qty Item Designation
019 - Piston ring, high, cermet type 1)
020 - Piston ring, high, cermet type 1)
032 - Piston ring, high, cermet type 1)
Note:
1)
When ordering, please state IMO no., engine type and
height of each ring.
2 (2)

MAN B&W 8872-2272-0011
Plate Special Instruction
8872-2272-0011
1 (2)

8872-2272-0011 MAN B&W
Plate Special Instruction
8872-2272-0011
Item No. Qty Item Designation
019 - Piston ring, high, cermet type 1)
020 - Piston ring, low, cermet type 1)
032 - Piston ring, low, cermet type 1)
Note:
1)
When ordering, please state IMO no., engine type and
height of each ring.
2 (2)